When microfilm was first developed as a means of copying records, the film commonly used for this purpose was unperforated 35mm film. The 35mm film was readily available and it was quite simple to secure the unperforated film so that the largest possible image could be secured. The quality of the lenses available was such that larger images were desirable.
Since then the optical systems and the film emulsions have both been improved and it is now customary to use 16mm film for the making of microfilm copies and the use of 8mm film is being considered. Except in special cases, 35mm film is not presently being used but instead smaller films are now used. It is obviously much more convenient to have all of the microfilm records on film of one size and, hence, many organizations are now converting their 35mm microfilms to 16mm or even 8mm microfilm records.
To effect this conversion, the 35mm microfilm records must be printed onto the smaller size film.
Conventional motion picture printers rely upon the perforations in the film to register the image, to insure its proper advancement, and to hold it immovable during the exposure. Since microfilm is not perforated, it is not possible to use the pins of the conventional motion picture film printer to register and advance the film and, hence, the usual step printing operation is not suitable for microfilm.
Furthermore, since the material that is conventionally recorded on microfilm is usually printing or other material having correspondingly fine lines, it is very important that the image formed on the camera film be very sharp and that there be no movement of the image with respect to the film at any time.